Electrical connections to conductors having thin film insulation

ABSTRACT

An electrical connection with a conductor having an extremely thin film type insulating covering thereon is formed by providing a terminal having a contact surface to which there is adhered fine particles of grit which are covered by a thin coating of a soft metal. The connection is made by sliding the conductor relatively over the terminal so that the film is scored and the metallic conductor is exposed. Contact between the terminal and the conductor is established through the soft metal which occupies the space between the conductor and the terminal surface.

United States Patent 1191 Evans et al.

[ June 18, 1974 [54] ELECTRICAL CONNECTIONS T0 3,014,140 12/1961 Tupper 339/97 R x CONDUCTORS HAVING THIN FILM 3,718,750 2/1973 Sayers 339/278 C X INSULATION R b L W 1f Primary Examinero ert o e [75] Inventors g t i g i H Assistant Examiner-Richard P. Tremblay i lgi isg g g i g Pa Attorney, Agent, or Firm-William J. Keating [73] Assignee. AMP Incorporated, Harrisburg, Pa. ABSTRACT [22] Filed: Feb. 16, 1973 An electrical connection with a conductor havlng an PP NOS ,242 extremely thin film type insulating covering thereon is formed by providing a terminal having a contact sur- 521 [LS Cl 339 17 F 339/97 R, 339 99 R face to which there IS adhered fine particles Of grit 339/278 C which are covered by a thin coating of a soft metal.

51 Int. Cl 110 11' 9/08, HOlr 3/00 The Connection made by Sliding the conductor rela- [58] Field of Search 339/97 R 97 P, 98 99 R, tively over the terminal so that the film is scored and 339/95 R, 95 P, 278 C 278 R, 17 F the metallic conductor is exposed. Contact between the terminal and the conductor is established through [56] References Cited the soft metal which occupies the space between the UNITED STATES PATENTS conductor and the terminal surface.

2,576,528 11/1951 Matthysse 339/278 C X 11 Claims, 15 Drawing Figures PATENTEB JUNI 819M SHEET 1 0F 5 PATENTEB JUN 1 81974 SHEET 2 OF 5 PAIENIEnJum 8 Ian SHEET 3 G? 5 PAIENIEnJuM I 81974 SHEET B [If 5 PAIENI [0 JUN 1 81974 SHEET 5 [IF 5 ELECTRICAL CONNECTIONS TO CONDUCTORS HAVING THIN FILM INSULATION BACKGROUND OF THE INVENTION This invention relates to electrical connections between terminal members and conductors, particularly very small conductors having a thin insulating film thereon.

A type of conductor which is being used to an increasing extent comprises an extremely thin ribbon-like metal strip having a thin film of plastic insulation thereover. Conductors of this type are used in flexible flat cables and in so called flexible circuitry and the trend is towards thinner and more narrow conductors as the size of solid state electrical devices decreases. Another type of conductor having a film type insulating coating is an extremely fine single strand wire, for example, AWG 36 or finer, having an insulating film such as a polyvinyl formal resin thereon. These film insulated wires have been widely used in the past for coil windings and are now being used for forming point-to-point interconnections among terminal members on a panel board, the terminals of which are extremely close together.

It has long been recognized that the formation of electrical connections with conductors having thin polymeric film insulating coatings thereon presents substantial problems which are not encountered where connections are to be made to relatively coarse conductors. Film type insulation is extremely tough and tenacious and is removed only with considerable difficulty. Mechanical stripping of these thin film type insulations as by the use of abrasive wheels is not satisfactory for the reason that any abrasion of the film is likely to damage a conductor. Some types of film insulation, particularly the polyvinyl formal resins, can be chemically stripped but processes of this type are awkward and time consuming.

When an electrical connection must be made to a fine conductor having a thin film insulation, further problems after the removal of the insulation because of the extremely small size of the conductor. Conventional mechanical crimps are used to some extent, particularly for wires, but these become impractical for extremely fine wires for the reason that the ferrule of the terminal which is crimped onto the wire becomes extremely massive as compared to the diameter of the wire. Furthermore, the conductors are extremely delicate and may be broken during the crimping operation.

I have found that a good electrical connection with a film insulated conductor can be obtained by providing abrasive particles on a terminal substrate in a manner which is described below and sliding the conductor over the terminal surface while the two parts are held against each other. The abrasive particles on the terminal substrate score the insulating film and cause it to rupture so that the metallic conductor is exposed. When the terminal and conductor come to rest, contact is established through the ruptured areas of the film. Connections in accordance with the invention can be provided for flat conductors having insulating film thereon such as the conductors of a flat conductor cable and for extremely fine film insulated wires.

It is accordingly an object of the invention to provide an improved electrical connection for film insulated conductors. A further object is to provide an electrical connection for a flat conductor having a film type insulating coating thereon. A further object is to provide an electrical connection for a drawn wire having a film type insulating coating thereon. A further object is to provide a terminal member or connecting member having a contact surface which can be electrically connected to a conductor having a film type insulating coating thereon by merely sliding the conductor over the surface. A further object is to provide a method of forming electrical connections with conductors having film-type insulated coatings.

These and other objects of the invention are achieved in a preferred embodiment thereof which is briefly described in the foregoing abstract which is described in detail below and which is shown in the accompanying drawing in which:

FIG. 1 is a perspective view of a fixture for forming electrical connections in accordance with the invention.

FIG. 2 is a perspective view of the terminal member of the fixture of FIG. 1.

FIG. 3 is a sectional view taken along the lines 3-3 of FIG. 1.

FIG. 4 is a cross-sectional view of the conductor shown in FIGS. 1 and 3.

FIG. 5 is a sectional view, on a greatly enlarged scale, of the electrical connection formed with the fixture of FIG. 1.

FIG. 6 is a fragmentary sectional view on a greatly enlarged scale of the contact surface of the terminal shown in FIG. 2.

FIG. 7 is a photomicrograph of the surface of a conductor of the type shown in FIG. 4 which has been electrically connected to a terminal as shown in FIG. 5 and which was then removed.

FIG. 8 is a fragmentary view illustrating an application of the invention to the formation of electrical connections between conductors on a panel board and conductors on a circuit unit having an integrated circuit therein.

FIG. 9 is a fragmentary exploded view showing structural details of the metallic supporting panel, the flexible circuit panel, and the circuit unit of FIG. 8.

FIG. 10 is a cross-sectional view of the circuit panel of FIG. 9.

FIG. 11 is a cross-sectional view of two terminal members in accordance with a further embodiment of the invention intended for making electrical connections to relatively fine wires having firm type insulating coatings thereon.

FIG. 12 is a fragmentary perspective view of a panel board. having terminals of the type shown in FIG. 11 therein.

FIG. 13 is a fragmentary perspective view showing a portion of a memory frame of a computer having a connecting means in accordance with the invention thereon.

FIG. 14 is a perspective view of the blank form which the connecting means is formed.

FIG. 15 is a perspective view of the formed connecting means.

The principles of the invention are described below with reference to FIGS. 1 6 which show a testing jig for testing electrical connections in accordance with the invention and the structure of the contact terminal of a connection in accordance with the invention. Specific applications of the invention are described hereinbelow with references to FIGS. 9 12.

In FIGS. 1 4, an electrical connection is formed between a conductor 2 and a terminal member 4 mounted on a fixture generally indicated at 5. The conductor comprises a metallic foil 6 having a thin film 8 of insulation material on each side thereof. The foil is advantageously of copper and has a thickness of about 0.0015 inch while the insulating films 8 may be of polyamidimid or Mylar (polyethylene terephthalate) and have a thickness of about 0.0008 inch. The terminal 4 is of sheet metal and has an ear l2 and a depending flange 10 on one side of which there is provided a contact zone which is described in detail below. The terminal is mounted on a pin 22 which in turn is mounted in a slidable block 18. The block 18 is contained in a central opening 16 ofa rectangular frame 14 and adjusting screws 20 are threaded into the frame to permit adjustment of the position of the block 18.

The conductor 2 is wrapped over one side of a support block 24 so that one surface 34 of the conductor will be brought against the contact surface of the terminal 4 when the block 24 is slid downwardly into the opening 16. The screws 20 are adjusted so that the contact surface of the terminal will bear against the surface of the conductor with a relatively light pressure, the pressure being such that the thin film conductor will not be torn or otherwise damaged.

The contact surface, FIG. 6, comprises a substrate 26 (the sheet metal of which the terminal is formed) having a thin plating 28 of a hard metal such as nickel on its surface. When this plating 28 is deposited, deposition is carried out in the presence of fine particles 30 of a hard abrasive material such as tungsten carbide so that the particles are embedded in the plating 28. As is apparent from FIG. 6, these particles project from the surface of the plating 28 but do not form a continuous layer; the surface thus has discrete particles thereon which are separated by flat expanses. A softer metal such as tin is then electro-deposited over the entire contact surface and forms a continuous blanket 32 which covers the particles 30 as well as the uninterupted surface areas of the contact surface. The sides of the particles and the thickness of the coatings 28, 32 are discussed in some detail below.

In order to form a connection in accordance with the invention, the block 24 is simply slid downwardly until it is in the opening 16 and during such movement, the surface 34 of the conductor is slid relatively over the contact surface of the terminal 4. During such sliding movement, the particles penetrate the coating 8 and score it as shown in FIG. 7 and the coating is broken or fractured in some areas to expose the conductor 6. The soft overplating 32 is displaced during this sliding movement and collects in those areas where the film is broken. After the block 24 comes to rest, continuity is thus established between the terminal and the conductor by way of the discontinuities or openings in film 8 and the collected soft plating material 32.

In order to achieve good results in the practice of the invention, the thicknesses of the platings 28, 32 and the size of the particles should be selected with reference to the thickness of the insulating film 8, the thickness, and therefore the robustness, of the conductor 6 and the amount of surface area available for contact. For example, where the terminal has a substantial thickness (0.004 inch) as compared to the conductor (0.001

inch) and the film 8 has a thickness of 0.0008 inch, good results are obtained with particles having an average size of about 21 microns. The plating 28 may have a thickness of about X 10 inches although the thickness of this plating will vary because of treeing effects which arise during the deposition. Larger particles are used if the coating 8 is relatively thicker than that of the conditions above and smaller particles might be used for thinner coatings.

The particles 30 are suspended in the bath while the plating 28 is being deposited and these particles simply become mechanically embedded on the contact surface. Alternatively, the particles might be sprayed against the surface as disclosed in US. Pat. No. 3,697,389 if the surface is relatively soft so that it can be penetrated by the particles. The plating 32 may be of a soft metal other than tin, for example, a soft gold. Under some circumstances, the plating 32 may be eliminated and contact will be obtained by direct engage ment ofthe connector 6 with the contact surface of the terminal. As noted above, the particles 30 do not form a continuous layer on the contact surface and it has been found that for the size of conductors discussed above, a particle density of about l50 particles per square milimeter will give good results.

Particles of the material other than tungsten carbide can be used in the practice of the invention. In general, the particles should be relatively hard and have sharp edges so that they will penetrate the insulating film of the conductor and tungsten carbide particles are well suited to the practice of the invention since they have these characteristics. The particles need not be conductive and ceramic particles can, therefore, be used. Nickel particles can also be used or other metal particles which are available in irregular shapes having sharp edges.

It wil be understood from the foregoing that the principles of the invention can be used to form electrical connections under a wide variety of conditions and the following specific examples merely illustrate the use of the invention for three commonly known situations in which a large number of connections must be made to relatively small conductors.

Referring to FIGS. 8 10, it is necessary in solid state circuit devices to form connections to integrated circuit units or chips and these chips are commonly encapsulated in plastic with metallic leads extending from the sides of the plastic material. In the FIG. 8, a chip is encapsulated in a circuit unit 36 which has terminal members 40 on its edges. These terminal members are connected in any suitable manner to the chip or chips which are contained in the circuit unit and the surfaces of the terminal members 40 are prepared as contact surfaces as discussed above. When the circuit unit 36 is to be connected to the conductors 38 of a thin circuit panel 41, the circuit panel is mounted on a firm support panel 44 having an opening 48 therein. The circuit panel, as shown in FIG. 10, has a plurality of conductors 38 contained in a film of insulating material and these conductors extend to the edges of a hole in the circuit panel.

The circuit panel 41 is positioned on the surface of the panel 44 and the edge portions of the circuit panel are turned downwardly against the flanges 48 of the support panel. The circuit unit 36 is then simply pushed downwardly into the opening 34 and the conductors of the circuit panel ,38 will be connected to the terminals 40 of the circuit unit.

Where connections must be made to extremely fine wires 56 (FIG. 11) having a thin film of insulation thereon, a cylindrical terminal member 50 is used which has a contact surface 52 in accordance with the teaching of the invention on its internal surface. The terminal member 50 of this embodiment has a contact pin 54 extending from its lower end so that the terminal can be disengageably coupled to a complementary receptacle.

To connect the wire 56 to the terminal 50, the wire is pushed down into the interior of the terminal by a stuffer 58 so that sliding movement of the wire over the contact surface 52 takes place and electrical contact is established. Terminals of the type shown in F IG. 11 can be used in a panelboard 60, FIG. 12, with the contact pin portions 54 projecting beyond the under surface of the panel board. The terminals can then be interconnected by routing wires between selected terminals and the inserted portions of each wire into the terminals as shown. Two or more wires can be connected to a single terminal by locating the wires at different positions on the plug 58. If the second wire must be connected to the terminal at a later time than the time at which the first wire is connected to the terminal, short plugs can be used as shown at 59 in FIG. 11. The panel 60 can be mated with a complementary panel board having contact sockets therein which are adapted to receive the ends 54 of the terminals or individual connectors having contact sockets therein can be mated with the rows of terminals on the underside of the panel board 60.

FIGS. 13 show application of the invention to the formation of electrical connections in a computer memory frame. The frame 66 has extremely small memory cores 62 on its upper and lower sides and fine wires 64 are threaded through these cores as shown. A connector block 68 of suitable insulating material is mounted on the end of the frame and has a strip connector device on its side. This connector device is manufactured by metallizing strip 70 of firm plastic at spaced apart locations 72 and preparing these metallized surfaces as contact surfaces having grit particles therein as explained above. Strip 70 is then folded as shown in FIG. 15 so that slots are formed which are lined with contact surfaces in accordance with the invention. The wires 64 are positioned in these slots and electrical connections are formed to the wires by virtue of the contact surfaces 72.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only.

What is claimed is:

1. An electrical connection between a conductor member and a terminal member, said conductor member comprising a metallic conductor having a thin polymeric coating thereon, said terminal member comprising a metal member having a contact surface,

said contact surface having thereon discrete fine particles of abrasive material, said particles covering a minor portion of said contact surface, and an electrodeposited coating of a soft conductive metal extending continuously over said surface and blanketing said particles,

said conductor member being against said contact surface, said polymeric coating being scored as a result of having been slid relatively over said contact surface, said coating being broken in discrete areas and said metallic conductor in said areas being in electrical contact with said contact surface, and

clamping means holding said conductor member against said contact surface.

2. An electrical connection as set forth in claim 1,

said coating of said soft conductive metal being of tin.

3. An electrical connection as set forth in claim 1, said conductor member comprising a flat ribbon-like metallic conductor.

4. An electrical connection as set forth in claim 1, said conductor member comprising a round wire, said terminal member comprising a hollow cylinder, said contact surface being on the interior of said cylinder, said wire extending into the interior of said cylinder, said clamping means comprising a member inserted into said cylinder.

5. An electrical connection between a conductor member and a terminal member, said conductor member comprising a metallic conductor having a thin polymeric coating thereon, said terminal member having a contact zone,

said contact zone comprising a conductive metal substrate, an electrodeposited first coating of a hard conductive metal in said substrate, discrete particles of an abrasive material embedded in and extending beyond said first coating, and

an electrodeposited second coating of a soft conductive metal extending continuously over said first coating and blanketing said particles, said conductor member being against said contact zone, said polymeric coating being scored as a result of having been slid relatively over said contact surface, said coating being broken in discrete areas and said metallic conductor in said areas being in electrical contact with said first coating, and

clamping means holding member against said contact zone.

6. An electrical connection as set forth in claim 5, said first coating being of nickel.

7. An electrical connection as set forth in claim 5, said second coating being of tin.

8. An electrical connection as set forth in claim 5, said first coating being of nickel, said second coating being of tin.

9. An electrical connection as set forth in claim 5, said conductor member comprising a flat ribbon-like conductor.

10. An electrical connection as set forth in claim 5, said conductor member comprising a round wire, said terminal member comprising a hollow cylinder, said contact zone comprising the interior surface of said cylinder said wire extending into said cylinder, said clamping means comprising a member inserted into said cylinder.

11. An electrical terminal means intended for connection to a conductor member, said conductor member comprising a metallic conductor having a thin polymeric coating thereon, said terminal member comprising:

8 surface and sliding said conductor member relatively over said contact surface, said particles penetrate said polymeric coating and said coating is broken, and electrical contact is established between said metallic con ductor and said contact surface. 

2. An electrical connection as set forth in claim 1, said coating of said soft conductive metal being of tin.
 3. An electrical connection as set forth in claim 1, said conductor member comprising a flat ribbon-like metallic conductor.
 4. An electrical connection as set forth in claim 1, said conductor member comprising a round wire, said terminal member comprising a hollow cylinder, said contact surface being on the interior of said cylinder, said wire extending into the interior of said cylinder, said clamping means comprising a member inserted into said cylinder.
 5. An electrical connection between a conductor member and a terminal member, said conductor member comprising a metallic conductor having a thin polymeric coating thereon, said terminal member having a contact zone, said contact zone comprising a conductive metal substrate, an electrodeposited first coating of a hard conductive metal in said substrate, discrete particles of an abrasive material embedded in and extending beyond said first coating, and an electrodeposited second coating of a soft conductive metal extending continuously over said first coating and blanketing said particles, said conductor member being against said contact zone, said polymeric coating being scored as a result of having been slid relatively over said contact surface, said coating being broken in discrete areas and said metallic conductor in said areas being in electrical contact with said first coating, and clamping means holding member against said contact zone.
 6. An electrical connection as set forth in claim 5, said firsT coating being of nickel.
 7. An electrical connection as set forth in claim 5, said second coating being of tin.
 8. An electrical connection as set forth in claim 5, said first coating being of nickel, said second coating being of tin.
 9. An electrical connection as set forth in claim 5, said conductor member comprising a flat ribbon-like conductor.
 10. An electrical connection as set forth in claim 5, said conductor member comprising a round wire, said terminal member comprising a hollow cylinder, said contact zone comprising the interior surface of said cylinder said wire extending into said cylinder, said clamping means comprising a member inserted into said cylinder.
 11. An electrical terminal means intended for connection to a conductor member, said conductor member comprising a metallic conductor having a thin polymeric coating thereon, said terminal member comprising: a contact surface having thereon discrete fine particles of abrasive material, said particles covering a minor portion of said contact surface, and an electro-deposited coating of a soft conductive metal extending continuously over said surface and blanketing said particles whereby, upon positioning said conductor member against said surface and sliding said conductor member relatively over said contact surface, said particles penetrate said polymeric coating and said coating is broken, and electrical contact is established between said metallic conductor and said contact surface. 